The 5-foot-7 brunette beauty does a combination of strength-training and cardio exercise to maintain her age-defying good looks.

“I do a lot of Pilates, kick-boxing and weight training in L.A., and when I’m in Austin [Texas], I run or ride a bike,” said Bullock.

Sandra, who has barely aged during the past 20 years, said staying in shape isn’t difficult because it’s her job to work out and look good. “People ask, ‘How do actresses do it [stay in shape]?’ ” Bullock said. “Um, they pay us to do this in order to look good on film.”

In recent years, Bullock has incorporated plyometrics and an hour-long routine that combines yoga, Pilates and fat-burning dance cardio workouts. The new regimen is clearly working, judging by her buff arms and toned torso.

Bullock’s trainer, Simone De La Rue, said Sandra’s super-fit physique is no accident: She works hard and is extremely disciplined.

Sandra puts in an hour a day [at the gym], six times a week,” said De La Rue, author of Body by Simone. “She is extremely motivated and driven.”

Bullock’s anti-aging fitness secret also includes a healthy low-carb diet. Low-carb diets such as the Atkins, ketogenic and Atkins diets promote rapid weight loss by inducing the body to burn fat for fuel, said obesity expert Dr. Eric Westman, co-author of Keto Clarity.

While she’s hailed for her age-defying beauty, Bullock is annoyed by the media obsession with aging.

“I feel like it’s become open hunting season in how women are attacked, and it’s not because of who we are as people, it’s because of how we look or our age,” said Sandra. “I’m shocked, and maybe I was just naive, but I’m embarrassed by it.”